The present invention relates to an amplitude detection circuit for generating output data responsive to the amplitude of an analog input signal and, more particularly, to such a circuit, of a digital construction, to generate digital output data.
An amplitude detection circuit is employed as an envelope detector of an analog input signal or a peak (or bottom) holder of an amplitude of the analog input signal. According to the prior art, the amplitude detection circuit includes an operational amplifier, a rectifier and a capacitor. The analog input signal is supplied to an input terminal of the operational amplifier whose output terminal is connected to the rectifier. The rectified signal derived from the rectifier is supplied to the capacitor, so that a detection signal is produced across the capacitor. The detection signal is supplied to a subsequent signal processor.
In a case where the subsequent signal processor is digitalized, an analog-to-digital converter converts the detection signal into digital data which, in turn, is supplied to the digitalized signal processor. In this case, two kinds of integrated circuit devices, an analog integrated circuit device used as the amplitude detection circuit and the second being a digital integrated circuit device used as the signal processor. Moreover, the analog integrated circuit device requires an external lead-out terminal for connecting the capacitor.